Number of tECSNe as a fraction of FeCCSNe, constrained by the solar ratio of key isotopes produced in the ejecta to oxygen. The minimum mass for FeCCSN was assumed to be m_l = 9 M_⊙. The dashed horizontal lines are the solar value for each isotope, which we take as an upper limit. The dashed vertical lines therefore indicate the upper limit on the number of ECSNe using each constraint from the solar abundances. The CCSN yields used were those of Nomoto et al. (2006) at metallicity Z = 0 (top row), Z = 0.001 (middle row) and Z = 0.004 (bottom row).